Electrode for arc-lamps.



F. 'KALKNER.

ELECTRODE FOR ARG LAMPS. APPLICATION FILED 4116.11, 1903.

Patnted M31130, 1909.

UNITED @FIE- FRIEDRICH KALKNER, 0F NUREMBERG, GERMANY, ASSIGNOR 'IO SIEMENS-SCHUCKERT WERKE G. M. B. 13., 0F BERLIN, GERMANY, A CORPORATION OF GERMANY.

ELECTRODE FOR ARC-LAMPS.

No. eiasw.

Specification of Letters Patent.

Application filed August 11, 1908. Serial No. 447,965.

To all whom it may concern:

Be it known that I, FRIEDRICH KALKNER, a subject of the German Emperor, and residing at Nuremberg, Germany, have invented certain new and useful Improvements in Electrodes for Arc-Lamps, of which the following is a specification.

The present invention relates to are lamps for large currents, particularly such as are used for projectors, arid an important object is to provide improved electrodes for the same.v It is known that the light yielded by these lamps, as well as the steadiness 0f the are can be increased by the cross-sectional area of the electrodes being reduced below the usual size. It is found in practice that the diminution of the cross-sectional area of the negat'ive'electrode alone sullices for obtaining the above mentioned result. Now it is not at once possible, however, to maintain the operation of the lamp for a rather long period with such an arrangement. On account of its small cross-sectional area the resistance of the negative electrode is so great that after a short time the electrode becomes red-hot along its entire length and is rapidly destroyed.

An important object of the invention is to overcome this defect.

In order that the invention may be clearly understood reference will be made to the accompanying drawing in which one embodiment is represented by way of example in elevation.

The above mentioned defect is removed in the following manner. The thin negative carbon rod n is covered with a jacket or casing m of copper or other suitable metal. The cross-sectional area of this good conducting metallic casing is chosen so large that the cathode is not heated injuriously when the current passes through it. the other hand the cross-sectional area of the carbon must be so dimensioned that the metal'lic casing is removed as soon as it arrives in immediate proximity to the are. If the negative carbon has a relativel lar e cross-sectional area which is approximate y equal to the sizes usual heretofore, parts of the meltin metal ass into the arc, temorarily cel o-r its lig names the steadiness of the lamp.

on I

t and prejudicially in-- The new arrangement according to this. I invention therefore differs substantially from former attempts to employ copper-plated l carbons, particularly bythis source of disturbance being removed by the crosssectional area of the negative-carbon being reduced to from one third to a sixth art of the size customary heretofore, and By the metallic casing being correspondingly increased in size. In this manner the result is obtained that the metallic casing is liquefied at a distance of from 2 ems. to 3 ems. from the arc and falls away in drops, so that Imetallie vapors do not pass into the are. How very much the cathode must be changed in this arrangement as compared with the form usual heretofore is readily understood when it is explained that the cross-sectional area of the new negative carbon for 150 ampercs, for example, amounts to only 0.8 sq. ems, whereas a standard cathode for this strength of current has a cross-sectional area of about 5 sq. cms. The advantages of this new cathode are available both in the known horizontal arrangement of the carbons, and also in the arrangement represented 'in the accompanying drawing. In the latter case the positive electrode 19 is horizontal and the negative carbon is arlranged at an angle of about 60 to the lhorizontal. This slanting position of the cathode facilitates and promotes in a particularly high degree the dropping oil 01' the li uefied metal. 7

l v What I clann as my invention and desire to secureby Letters Patent is:

In an arc lamp, the combination of a negative carbon which is relatively much smaller than the positive carbon, with a relatively thick metallic casing surrounding said negative carbon, substantially-as do- I scribed.

In testimony whereof I have signed my name to this specification in the presence of two witnesses.

FRIEDRICH KALKN ER.

Witnesses:

JACOB BIERLEIN, H. W. HARRIS. 

